issue12577.go

     1  // run
     2  
     3  // Copyright 2015 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Issue 12577: Test that there are no -0 floating-point constants.
     8  
     9  package main
    10  
    11  import "math"
    12  
    13  const (
    14  	z0 = 0.0
    15  	z1 = -0.0
    16  	z2 = -z0
    17  	z3 = -z2
    18  )
    19  
    20  var (
    21  	x0 float32 = z0
    22  	x1 float32 = z1
    23  	x2 float32 = z2
    24  	x3 float32 = z3
    25  
    26  	y0 float64 = z0
    27  	y1 float64 = z1
    28  	y2 float64 = z2
    29  	y3 float64 = z3
    30  )
    31  
    32  func test32(f float32) {
    33  	if f != 0 || math.Signbit(float64(f)) {
    34  		println("BUG: got", f, "want 0.0")
    35  		return
    36  	}
    37  }
    38  
    39  func test64(f float64) {
    40  	if f != 0 || math.Signbit(f) {
    41  		println("BUG: got", f, "want 0.0")
    42  		return
    43  	}
    44  }
    45  
    46  func main() {
    47  	if f := -x0; f != 0 || !math.Signbit(float64(f)) {
    48  		println("BUG: got", f, "want -0.0")
    49  	}
    50  
    51  	test32(-0.0)
    52  	test32(x0)
    53  	test32(x1)
    54  	test32(x2)
    55  	test32(x3)
    56  
    57  	if f := -y0; f != 0 || !math.Signbit(f) {
    58  		println("BUG: got", f, "want -0.0")
    59  	}
    60  
    61  	test64(-0.0)
    62  	test64(y0)
    63  	test64(y1)
    64  	test64(y2)
    65  	test64(y3)
    66  }
    67
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